Mexico's cuisine has long been overshadowed by the greasy Tex-Mex burritos and nachos sold around the world, but efforts to refine its image are now beginning to pay off.

Five months after Mexican gastronomy joined the ranks of pre-Hispanic monuments winning special recognition from the United Nations cultural body, UNESCO, a restaurant serving up Mexican dishes has for the first time been named among the world's top 50 eateries.

Pujol joins another restaurant also in an upscale district of Mexico City, which serves up Basque fusion cuisine, which made it to the list in 2010.

Since pre-Hispanic times, Mexican dishes have drawn on a wealth of ingredients, including many varieties of corn, beans and chili peppers, as well as native tomatoes, avocados or cocoa.

But top chefs are increasingly mixing up traditional recipes to give them a modern twist.

"People think that Mexican food is heavy, that you have to go on a diet of lettuce three days before you eat it," says Enrique Olvera, owner of Pujol which made the S. Pellegrino World's 50 Best Restaurants list in April.

"We're looking for a new experience," Olvera says, using tweezers to assemble a starter of bean dip, roast tomato skin, zucchini, cheese, oil from the Pipicha herb - similar to cilantro - and tiny toasted Jumiles bugs.

The 35-year-old has inspired a generation of Mexican chefs and won widespread acclaim in the 11 years since Pujol opened.

The minimalist restaurant is located in the capital's Polanco district, also home to Biko, a Basque restaurant and the only other one in Mexico ever to make the top 50 best restaurants list.

Pujol recently received a visit from Irish rocker and U2 frontman Bono, who chose to celebrate his birthday there.

"The fact that there's a Mexican restaurant in the top 50 means that the world is changing," says Olvera.

A new gastronomy festival in Morelia, Michoacan, in western Mexico, at the end of May, aims to give their efforts a further boost.

Smart restaurants and cooking schools here have long favored foreign cooking, particularly from France, but Mexican cooking classes have increased in recent decades.

Attitudes to Mexican food "have changed a little, but it's a question of self-esteem", says Yuri de Gotari, who opened the small School of Mexican Gastronomy in Mexico City in 2007.

"People are slowly realizing that they have valuable ingredients," De Gortari says, as he demonstrated a molcajete - a Mexican stone version of the mortar and pestle - to a class of students.

Key to Mexican cooking, fresh ingredients are still sold in markets across the center and south of the country, where traditional dishes are also found.

Prickly pear cacti, yellow zucchini flowers, dark red hibiscus flowers and tropical fruit including the endemic mamey sit alongside delicacies such as grasshoppers on market stalls.

But, as elsewhere, a proliferation of junk food is threatening culinary traditions.

Many hope UNESCO's special recognition of Mexico's entire national cuisine in November, along with French gastronomy and the Mediterranean diet, will help raise awareness of threatened culinary traditions.

"One thing you're seeing is more restaurants promoting local ingredients, which you didn't even see when I got here two years ago," says Lesley Tellez, a joint founder of Eat Mexico, a company offering street food and market tours.

Agence France-Presse